Antiinflammatory drugs such as steroids have been conventionally used as symptomatic therapy in the treatment of autoimmune diseases and the like, but better radical therapy for these diseases is needed. In addition, abnormal changes in the immune system have been reported in relation to the incidence of diabetes mellitus and nephritis (for example, refer to Non-patent Literature 1 and Non-patent Literature 2). However, no drug that ameliorates abnormal changes in the immune system has been developed to date.
On the other hand, it is important to develop a method to suppress immune responses not only for preventing rejection symptoms in organ transplants and cell transplants but also for preventing as well as treating various autoimmune diseases. However, since previously known immunosuppressants such as cyclosporin A (CsA), tacrolimus (TRL), and the like are known to exhibit liver and kidney toxicity, concomitant use of a steroid or the like has widely been used to suppress such side effects. On the other hand, a significant immunosuppressive effect without side effects has not yet been obtained.
Based on this background, many attempts have been made to discover an agent that exerts excellent immunosuppressive activity with low toxicity. The following reports describing the background of the present invention are disclosed. present invention are disclosed.
For example, the following compounds shown below are disclosed in Patent Literature 1.

For example, the following compounds shown below are disclosed in Patent Literature 2.

For example, the following compounds shown below are disclosed in Patent Literature 3.

For example, the following compounds shown below are disclosed in Patent Literature 4.

For example, the following compounds shown below are disclosed in Patent Literature 5.

For example, the following compounds shown below are disclosed in Patent Literature 6.

However, the chemical structures of the compounds disclosed in the literatures from Patent Literature 1 to Patent Literature 6 described above differ from those of the compounds of the present invention.    [Patent Literature 1] International publication number WO 03/062252 (US2005/0033055)    [Patent Literature 2] International publication number WO 03/105771 (US2005/0245575)    [Patent Literature 3] International publication number WO 2004/058149 (US2006/0161005)    [Patent Literature 4] International publication number WO 2004/103306 (US2005/0014728)    [Patent Literature 5] International publication number WO 2004/103309 (US2005/0014724)    [Patent Literature 6] International publication number WO 2005/000833 (US2005/0014725)    [Non-patent Literature 1] Kidney International, Vol. 51, 94 (1997)    [Non-patent Literature 2] Journal of Immunology, Vol. 157, 4691 (1996)